Siemens S5-100U User Manual page 65

Installation Guidelines
Chassis Grounding of Inactive Metal Components
Correct chassis grounding is an important factor in ensuring that you won't experience interference
problems. Chassis grounding refers to the conductive connection of all inactive metal components
(VDE 0160). Always use surface-contact grounding. Chassis-ground all inactive metal components.
Basic rules for surface-contact grounding:
• All chassis connections should have a low impedance.
• All metal components should have a large surface contact.
- Use especially wide grounding strips when you connect the components. The surface area of
the chassis ground is the deciding factor and not the cross-section of the interconnecting
cable.
• Use spring lock washers or serrated lock washers on all screwed connections.
Filters for Main Cables and Signal Cables
Filtering main cables and signal cables is a means of reducing conductive-associated interferences.
No overvoltages may be allowed to occur in the supply lines and signal cables located in a cabinet.
Use the following procedures to avoid having overvoltages occur:
• Interference suppression in main cables
A main filter (e.g., B84299-K64, 250 V AC/10 A) should be installed in the supply line for
incoming supplies from the main supply. Always install the main filter on the cabinet opening.
When you install the main filter, make certain that it has a large surface contact and a low
impedance to the cabinet's chassis ground. Make sure that the contact surfaces are bare.
• Discharge capacitors for a DC power supply
If a cabinet is connected to a central 24-V power supply, then noise interference can pass into
the control system via this supply line.
This can be avoided by installing interference-suppression capacitors on the cabinet opening of
the 24-V supply. Mount these capacitors either on the cabinet's chassis ground or on the
shielding rail.
Figure 3-25 shows the layout of the interference-suppression capacitors.
e.g. 0.6
B81551-A-B16
+24 V
Figure 3-25. Layout of the Interference-Suppression Capacitors
EWA 4NEB 812 6120-02
F
µ
0 V
Cabinet's chassis
ground
e.g. 0.2 F
µ
B81111-A-B42
+24 V
S5-100U
Block diagram
0.2 F
µ
0.6 F
0.6 F µ
µ
0 V
3-33